Hitachi 42HDS52 When powers off has to unplug to power on

[jason123]

I was wondering if someone could guide me through the repair of a Hitachi 42HDS52 TV. It has a great picture quality and unfortunately it works great as long as I don't turn it off. Whether it's with the button or remote, once I turn it off, I can't turn it back on unless I unplug from the wall, then re plug it back in then it would turn on. Any thoughts on where to even start?

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Just got around to really see what's going on... When plugged in, the light (power indication) is solid red. When I push the power button, it turns green. Then it blinks green 7 times. then 2 times. Then solid green, but no picture, however sound is on and TV is responsive to vol+ / Vol -. Where can I find the error codes / blinks on this TV? I have the service manual, but no info on error codes.
Thank you

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Usually on these Hitachi plasmas, if the tv turns on with sound, the fault is that a fault with the vs or va voltage was detected. If you monitor the vs or va you will see the voltage come up and then drop off. Normally this would be a faulty buffer board or Ysus board, but if the tv does still come on with a good picture, check what the vs and va voltages are.
I think this model had some problems with the large caps on the power supply board that supplies the vs voltage, if they are bad/weak then that could be the problem as to why it wont start but when it does it stays on.
I believe the green led flashing is normal when the tv first starts up.
Provide a couple of clear pictures of the boards, especially the power supply board
I have this that might help but if your tv picture does come on I would say buffers are fine, ysus, might have a bad cap somewhere, or power supply has cap issue

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Thank you R_J
I will review the guide and share some photos this afternoon. Appreciate your help.

Picture used to come one on unplugging and re-plugging. Now, I only get sound. Occasionally, the Green LED comes one steady (Usually after unplugging for a while) and other times it comes on with the blinking, as described earlier. I'm curious as to why Hitachi doesn't make the error blink codes available. I looked everywhere online and I can't seem to find a decoder for the blinking codes.
Thank you

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

a quick update. After being unplugged for a while, upon plugging in, Vs / Va (CN64 1 and 10) attempt to come up (fraction of a second - DMM can't capture - Simply starts going up and before settling goes back to 0)
It does that with both the X/Y Sus boards plugged in (normally) or unplugged. Leads me to believe, maybe PS board is bad? I measured the resistance on the connector (when unplugged from the PS board) for Vs and Va, and they're high (not short certainly) - not sure if this is a valid test to make sure the short is not on the x/y sus boards?
No swollen caps on the PS board and ESR on the large caps is sub miliohm. Nothing noteworthy on the photos, other than some dust, but included as requested. Thank you

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

What usually goes on these sets is one ore more buffer ic's on the buffer boards, usually but not always the upper buffer board, you could disconnect the buffer boards from the ysus, you can leave them connected to the panel, and see if the vs voltage stays up.

If the power supply vs & va does come up and then drop off I quite sure the power supply is o.k.

The ysus can fail without there being a dead short on the supply, if there was a dead short the voltage would not come up at all.

There are ways to check the buffer board ic's for shorts, The pdf has a quick way to test

I can't remember exactly but you place one probe on one of the pins that go to the ysus and with the other probe check the pins on the plug going to the panel (there are 2 rows of pins on each panel plug) there should not be any shorts to those pins if there are the buffer ic is bad.

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Thanks R_J will check on these guides shortly

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Hi R_J,
I went through all pdfs you sent. Thank you, they're very helpful. My TV is chassis DW1-UB, and is a bit different in the sense that, for example, I don't have the large blue caps on the buffer board (Connected to Ysus) - See photos.

To force voltages on, guide for DW-1, states to short CN63 Pin 3 (5V STB) to 6 (STBY2)and 7 (STBY3) (of the same connector I'm assuming). However, pin 6 and 7 of CN63 in the service manual has pin 6 and 7 labeled as 3.3V. Is it safe to short these, or do I have the wrong manual (attached)?

Finally, they're instructing to measure the impedance from Vs and Va (to GND), and I'm getting infinite reading and no physical damage to the buffer board ICs (see photos) - the guide still suggests that the problem is in the logic board (not issuing the right turn on commands) and no mention of PS failure as an option, like you stated. Could it be the logic board if the front LED turns green (blinks then stays green)? that wasn't very clear in the No Picture Troubleshooting Guide. Thoughts?

Thank you again for the help

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Quick update.. 16 V is showing up as 14.55 V (maybe within range?)
24 and 10 are fine

when I attempt to force VS and VA to come on, 0 voltage appear (though it tries to come up, with the VS VA connector disconnected) then the whole system shuts down

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

That first test says the power supply must already producing stb5v (cn63 pin1) stb 3.3V (cn63 pin 3)
CN63 PIN 1 is stdby 5.4 volts (do not use pin 1)
So the first Test is to short CN63 pin3 (3.3v) to pin cn63 pins 6&7 (3.3v) This is to check the 10,16 & 24 volts
(using the 42"model directions)
the second test is to check the Va,Vs voltage by unpluging cn68 and short cn68 pin3 (stby3.3) to pins 7&8
pins 7&8 on the power supply need to be 3.3 volts for the Va,Vs to turn on, these voltages normally come from the logic board and I am 99% sure the logic board is fine and the fault is either Ysus, upper, lower buffer or all 2 or 3
Did you try unpluging the upper and lower buffers from the Ysus and see if the Vs stays up?

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Hi R_J, the first test, I completed.. and it worked fine with the exception that the Voltage on the 16 V was 14.55 V. The supply is producing stb5V and 3.3

I did try unplugging the entire Xsus, Ysus, and finally just unplugging the upper and lower buffers (see photo) and no change. Vs and Va are not coming on or staying on.

Thoughts?

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Just a note, I did order a power supply and it came in.. the first time I installed it and powered up the system worked.. so I thought it fixed it.. but it was one of those rare times where the system did come on.

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

You can adjust it, it won't make that much difference. those power supplies were usually quite reliable.
Just saw your last post. So if it does not come on do you still have audio?
If it works sometimes I would think the buffer boards should be o.k. They usually short and don't become intermitint. so It could be something on the Ysus

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

False Alarm R_J.. it didn't fix it.. just worked the first time I put the power supply in. No luck after that first time.

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

there are 2 connectors connected to the Xsus (buffers maybe?).. should I try disconnecting those and powering up?

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

I would leave those panel connections to the Xsus connected, they are not buffers they are just solid copper connectors that go to the panel.
I guess you could remove the ysus and check for poor solder connections, I would check the connections on the transistors etc. that are mounted to the heatsinks, sometimes the larger connections don't get enough solder when they are manufactured and over time they can become intermitint. but again these boards are built quite good. You could also check the xsus for the same poor connections.

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

what's odd.. is the Vs Va forcing the voltage test, doesn't result in Vs and Va to come on and stay on. They come on for maybe 5-10 seconds, then a relays kicks in and they go off. The test sheet doesn't seem to mention that.
So in your opinion, replacing the ysus might take care of it?

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

sound / audio always comes on by the way

[R_J]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

I can't remember, do you have the cable disconnected between the power supply and the Ysus when you did the test? I think it should stay up
It's hard to guess where the problem is, if it works sometimes, something is just borderline the fault could be on the Ysus or Xsus, I would pick Ysus first
These sets were a pain in the ass repair and there were'nt that many around like the other brands.
almost no information and no schematics for the panel boards.
I also have this bulletin

I have 2 55HDT52 both need buffer boards and one also needs Ysus. even if I repaired them they have little value, unless you own a boat

[jason123]

Re: Hitachi 42HDS52 When powers off has to unplug to power on

Yes, R_J, I did try disconnecting the power cable to the Ysus. No change, the Vs and Va would not come up. I inspected both the Ysus and Xsus.. they seem to be in good order, no thermal stress on the power transistor pins or joints.

If only I could find what that error code (green blinks of 7 then 2) means. They go through the trouble of generating codes but they don't tell techs what they mean?